Role of Defects in the Transport Properties and Photoresponse of a Silicon–MoS2 Mixed-Dimensional Van der Waals Heterostructure

Abstract

Heterostructures based on two-dimensional (2D) materials have demonstrated huge potential in various modern-day electronic and optoelectronic devices, but their optoelectronic properties are strongly influenced by the defects present in these materials. Hence, an in-depth understanding of the role of defects is vital in designing high-performance optoelectronic devices. Here, we investigated the role of defects in the electronic transport and photoresponse properties of a silicon–MoS2 p–n junction heterostructure through temperature-dependent electrical studies and demonstrated a method for improving their photoresponse. The presence of space-charge-limited transport with exponentially distributed trap states was evident from the temperature-dependent I–V characteristics. The temperature dependence of the ideality factor and intensity-dependent photoresponse also elucidated the nature of defects. The amplitude of low-frequency 1/f noise was observed to decrease with an increase in temperature, revealing the significant influence of defects on the charge transport. These defects can often cause recombinations, diminishing the photoresponse and severely degrading the optoelectronic properties. A significant enhancement in photoresponse by reducing the recombination centers was obtained by altering the surrounding dielectric environment. For a particular dielectric, the enhancement was observed to be more prominent toward low temperatures. In addition, the surrounding dielectric also effectively suppressed the low-frequency noise levels in the heterostructure. Insights from this study would help in designing and improving the properties of low-dimensional optoelectronic devices.